A 96-well based analysis of replicon elimination with the HCV NS5A replication complex inhibitor daclatasvir

A 96-well based replicon elimination and colony formation assay is presented for comparing the resistance barrier of the hepatitis C virus (HCV) NS5A replication complex inhibitor daclatasvir (DCV, BMS-790052) on three HCV genotypes (gts) in a proof of concept experimental protocol. The 96-well assay format provides both individual colony as well as population characterization and is readily applicable to other HCV direct-acting antiviral agents (DAAs). The assay provides an assessment of HCV replication levels over a 5log10 range by measuring a luciferase reporter resident in the HCV replicons. Individual colony status can be measured with a separate and compatible resazurin assay to assess relative host cell fitness following inhibitor treatments. The methods employed are non-toxic and leave intact isolatable colonies that can be used for phenotyping and genotyping. The utility of the assay is demonstrated by the identification and isolation of resistant variants as well as in the ranking of the relative resistance barrier for the replication complex inhibitor DCV for gts 1a, 1b and 2a. The format provides a quantitative ranking based upon luciferase activity and has the ability to monitor DAA resistance development over time for large numbers of compounds.